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Y4 Obstetrics and Gynaecology > Pregnancy - small for dates > Flashcards

Pregnancy - small for dates Flashcards

1
Q

What are the 2 primary causes of a small baby ?

A
  1. Pre-term birth (so normal for their gestation, its just that they are young)
  2. Small for gestational age (SGA)
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2
Q

Define what pre-term delivery is and the 3 sub-classifications of it

A

Defined as delivery between 24 & 36+6 weeks:

  • Extreme preterm: 24 – 27+6 weeks
  • Very preterm: 28 – 31+6 weeks
  • Moderate to late preterm: 32 – 36+6 weeks
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3
Q

What happens to the survival rate of pre-term pregnancies as they decrease in prematurity i.e. get older

A
  • Survival rate increases the less premature they are
  • Beyond 32 weeks >95% survival
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4
Q

List the causes of pre-term delivery

A
  • Infection
  • ‘Over distension’; Multiple pregnancy, polyhyraminos
  • Vascular; Placental abruption
  • Intercurrent illness; Pyelonephritis / UTI, Appendicitis, Pneumonia
  • Cervical incompetence - cervix dilates before pregnancy has reached term
  • Idiopathic (unknown)
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5
Q

List the risk factors for pre-term birth and highlight the 2 main ones to know about

A
  • Previous Pre-term labour (20% risk X1; 40% X2))
  • Multiple (50% risk)
  • Uterine anomalies
  • Age (teenagers)
  • Parity (=0 or >5)
  • Ethnicity
  • Poor socio-economic status
  • Smoking
  • Drugs (especially cocaine)
  • Low BMI (<20)
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6
Q

what are the 4 main ways pre-term labour presents ?

A
  • 25% planned caesarean section - Severe pre-eclampsia, kidney disease or poor fetal development.
  • 20% premature rupture of membranes (PROM)
  • 25% emergency event - Placental abruption, infection, eclampsia
  • 40% cause unknown
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7
Q

What are the symptoms suggestive of pre-term labour ?

A
  • Contractions
  • Rupture of membranes (can happen a fair bit before labour starts)
  • Brownish or blood tinged mucus discharge
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8
Q

How is PROM diagnosed ?

A
  • 1st line = Speculum exammination - if amniotic fluid pooling seen offer management, if none seen then:
  • 2nd line = Consider performing insulin like growth factor binding protein-1 test or placental alpha-microglobulin test of vaginal fluid

If both +ve then give antibiotics, if only insulin or placental alpha test +ve then consider their clinical condition & if neither +ve then reassure PROM is unlikely

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9
Q

If PROM suspected and labour has already been established, should you carry out the diagnostic tests for PROM?

A

No

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10
Q

What is the management of PROM?

A
  • 80% of PROM will initiate labour but in 20% it will not & may take a while before labour starts
  • If labour has initiated then management is that of pre-term labour
  • If labour does not initiate then there is now a risk of developing infection (due to ceale being broken) ==> antibiotics are given
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11
Q

What antibiotics are given for PROM when labour has not initiated ?

A
  • 1st line = erythromycin (max 10 days until labour established)
  • 2nd line = penicillin (if erythro not tolerated)
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12
Q

What is the management options for cervical incompentence ?

A
  • For women between 16 to 27+6 weeks with a dilated & exposed, unruptured fetal membranes a rescue cervical cerclage (cervical stitch) can be done
  • Contraindicated if signs of infection, active vaginal bleeding or uterine contractions
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13
Q

Does initiations of contractions always lead to pre-term labour ?

A

No - in 50% of cases contractions cease spontaneously & treating the cause e.g. pylonephritis may make it cease

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14
Q

What is the management of pre-term labour ?

A

Treat underlying cause if possible e.g. pylonephritis and it may cease

Give glucocortiocosteroids - for all at risk of iatrogenic or spontaneous pre-term birth between 24 & 34+6 weeks and consider for suspected or established pre-term labour, those having elective pre-term birth or who have prelabour PROM between 24 & 35+6 weeks (note need roughly 24hrs to work prior to the actual delivery)

Tocolytics (anti-contraction drugs) - for pregnancy with intact membranes & are in suspected or diagnosed preterm labour:

  • 1st line = nifedipine
  • 2nd line = oxytocin receptor antagnosit e.g. atosiban if nifedipine contraindicated

IV Magnesium sulphate (MgSO4) - for neuroptoection of baby when in established pre-term labour or having a planned one within 24hrs between 24 & 33+6 weeks

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15
Q

When is use of nifedipine contraindicated for pre-term labour ?

A

If the women has heart disease

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16
Q

What are the side effects of nifedipine ?

A
  • Decreased BP
  • Facial flushing
  • Headache
  • Increased pulse
  • Very rarley MI
17
Q

Why is it important to differentiate between babies who are premature and those who are SGA, why?

A

Because they are at risk for different problems following birth

18
Q

What are the 2 causes of a baby being small for their gestational age (SGA)?

A
  1. Intra-uterine growth restriction (IUGR) - this is pathological
  2. Baby is constitutinally small (familial)
19
Q

Define what small for gestational age (SGA) is

A

This is an infant with a birthweight that is less than the 10th centile for their gestation when compared to general population & customised growth charts (corrected for maternal height, weight, fetal sex & birth order)

20
Q

Define what low birth weight is

A

LBW = birth weight below 2.5 kg (regardless of gestation)

21
Q

What can IUGR broadly speaking be due to problems with what 3 main things ?

A
  1. Maternal
  2. Fetal
  3. Placental
22
Q

What maternal factors can lead to IUGR ?

A
  • Lifestyle; Smoking, Alcohol, Drugs
  • Height and weight - BMI < 20
  • Age ≥ 40
  • Maternal disease e.g. HTN, renal impairment, DM, PET
23
Q

What fetal factors can lead to IUGR ?

A
  • Infection e.g. Rubella, CMV, toxoplasma
  • Congenital anomalies e.g. absent kidneys
  • Chromosomal abnormalities e.g. Downs syndrome
24
Q

What placental factors can lead to IUGR ?

A
  • Infarcts
  • Abruption
  • Often secondary to HTN
25
Q

IUGR implies a pathological restriction of the genetic growth potential of a fetus, as a result IUGR fetuses may manifest evidence of fetal compromise which may be indicated by what?

A
  • Abnormal doppler studies
  • Decreased liquor volume
26
Q

What are the potential consequences of IUGR ?

A
  • Antenatally/ in labour - risk of hypoxia &/or death

Postnatally:

  • Hypoglycaemia
  • Effects of asphyxia
  • Hypothermia
  • Polycythaemia
  • Hyperbilirubinaemia
  • Abnormal neurodevelopment
27
Q

What are the clinical features suggestive of IUGR ?

A
  • Predisposing factors
  • SFH < than expected
  • Reduced liquor (oligohyraminos)
  • Reduced fetal movements
28
Q

What is done to assess fetal wellbeing (survellience of a SGA baby)?

A
  • Assessment of growth
  • CTG
  • Doppler US

Biophysical profile (now not done)

29
Q

How is the growth of a fetus assessed ?

A
  • Initially use SFH and plot measurements against centile charts at each antenatal appointement from 24 weeks
  • If growth restriction suspected (AC or EFW below the 10th centile) then monitor growth with serial U/S of head & abdominal circumference
30
Q

How is a CTG assessed in the assessment of a SGA ?

A

DR C BRAVADO - covered in another lecture

31
Q

Serial growth scans and CTG are used in the assessment of a SGA baby but what is the primary survellience tool?

A

Umbilical artery doppler (middle cerebral artery doppler & ductus venous suppler also used) - it is used to measure placental resistance to blood flow

32
Q

Go over these points on US assessment of a SGA baby

A
  • Umbilical artery should be low resistance but if compromised becomes high resistance, so flow becomes absent or even reversed in diastole.
  • Ductus venosus becomes pulsatile and increases its resistance.
  • Middle cerebral artey decreases its resistence to maintain blood flow to fetal brain.
33
Q

When should a SGA baby be delivered ?

A

If all well deliver by 37 weeks

Indications for considering earlier delivery by caesarean section:

  • Growth becomes static (IOL may be appropriate)
  • Abnormal umbilical artery Doppler
  • Normal umbilical artery Doppler with abnormal MCA between 32 and 37 weeks
  • Abnormal umbilical artery Doppler with abnormal ductus venosus Doppler between 24-32 weeks

Note - Delivery of the SGA infant is a balance between the risks of prematurity and the potential of hypoxia in utero or still birth.

Y4 Obstetrics and Gynaecology (63 decks)

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